Motion converting apparatus or devices are used in a wide variety of environments. In particular, oscillating fluid-driven actuators can be used when a device is required to impart rotational force to another member. Such oscillating fluid-driven actuator can be manufactured in a variety of sizes depending on their application.
These actuators are ideal, although not limited to, equipment that requires high torque to rotate, such as for example bulk material handling systems. Hydraulic oscillators are utilized at mining sites that use large conveyer booms to load silos, trucks, trains or ships. The rotation of the boom is essential for the efficient positioning and loading and unloading of the material.
Oscillating fluid-driven actuators can be located at one end of the boom and can be rotationally driven about an axis to locate the conveyor boom at the desired location. Rotational movement of these oscillators is generally accomplished by rotational movement of a piston within an annular chamber. Trunnion hubs have been added to the actuator to permit vertical movement of the boom.
Oscillating fluid-driven actuators may be secured to land, on ships or other vehicles, or the like. Generally speaking oscillating fluid-driven actuators that have been secured to ships having large conveyor booms in their bulk material handling systems also utilize rack and pinion arrangements with the actuators when rotating the boom as such heavy output booms require high torque to rotate the booms during operation.
However, actuators having rack and pinion arrangements require large surface areas and therefore restrict the ships capacity due to size and space limitations of the deck covers. Such deck covers are required to be opened for loading, yet the size of the covers is limited by the external turning dimensions of the actuator due to its close proximity to the deck. The loading capacity of the ship may be increased by reducing the turning radius of the equipment.
Conventional ship steering can also be accomplished by rack and pinion structure or hydraulic cylinders. These units require hydraulic induced force. In such applications, the oscillator is fixed while allowing the internal pin or shaft to rotate about an axis which accordingly is attached to the rudder giving the ship's steering capability.
Various devices have heretofore been designed incorporating the actuators generally described above. For example. U.S. Pat. No. 4,982,680 relates to an hydraulic wing actuator for turning movement of a spindle comprising a lower part fixed to the ship hull and an upper part secured to the lower part and which together define a substantially torus shaped guiding path.
Moreover, U.S. Pat. No. 3,446,120 relates to an oscillating fluid-driven actuator having an annular segment-shaped piston slidable mounted in an annular segment-shaped chamber. The piston is integrally formed with an arm and a hub which in turn is operatively connected to a rotary shaft. A fitting plate carries a sealing member at one end or both ends of the piston and is connected to the piston to allow the plate radial movement on the pistons, whereby the sealing member is maintained in central bearing engagement with the chamber.
Furthermore, U.S. Pat. No. 3,731,597 illustrates another rotary actuator.
It is an object of this invention to provide an improved oscillating fluid-driven actuator. Furthermore, it is an object of this invention to provide a oscillating fluid-driven actuator having improved turning characteristics when utilized on ships.
Another difficulty experienced by prior art actuators resides in the leaking characteristics experienced by the fluid mechanisms utilized in the high pressure fluid systems. Many of the prior art actuators include sealing structure in the corners of an annular chamber which are difficult to accurately manufacture and assemble, and therefore eventually leak or ultimately fail in operation. Various attempts have been made to improve such seals. For example, U.S. Pat. No. 3,750,535 relates to a rotary actuator having seal material of synthetic resin which is provided in the internal periphery of the cylinder and the shaft. However, leaking of the seals still plague actuators manufactured in accordance with present standards.
It is a further object of this invention to provide an improved sealing structure when utilized with the actuator described herein.